A variety of battery pack generate power from multiple interconnected batteries. These battery pack employ a holder to hold the batteries in position relative to one another. The batteries and holder are then positioned in a case for the battery pack along with other components such as cooling plates, electrical adapters, and other electronics. Since the case, holder, and other components take up space, these battery packs can be associated with an undesirably low energy density. As a result, there is a need for an improved battery pack.